I think the older established areas like Walnut Knolls, Starlite Hills, etc., are less affected by the train noise than say the new KB and Robson developments because they are literally 30-200 yards away from the tracks. I help manage a little league team here in Warm Springs and have children in the local schools and I can tell you we vaguely here the train horn in the mornings and afternoons, but that's about it. Also as a Realtor and home owner in the area the train, freeway, and busy intersection affect resale value so this is something to be mindful of. The good news is there are several homes in the area that are in good locations so you don't have to worry about selection being a problem.
Also be aware that they are starting to improve major intersections whereby the road will go over or under the train, thereby reducing the need for horns.
As the realtors would say "do your research"